You can drive a truck through the gap this thing
leaves between the wafer and the mask, esp
on the left side. It's like millimeters, when it's
supposed to be 30 micron.
At first, the mask wouldn't load (vacuum error). Finally,
after half a dozen retries, it loads. Problem may have been
due to wedge problem too (if it can't get mask parallel
to holder, then it can't pull the vacuum?).